Compressor for an aircraft engine

Abstract

On a compressor with compressor blades, a flow transition fixation mechanism ( 4 ) is provided on the suction side ( 2 ), approximately parallel to the leading edge ( 3 ) and upstream of the compression shocks acting upon the blade, which prevents the transition point from the laminar to the turbulent boundary layer flow from oscillating, thus suppressing oscillation of the compression shocks and their coupling effect with the natural frequencies of the compressor blades.

1. An aircraft engine compressor having compressor blades attached to a compressor disk, which compressor blades, under operating conditions, are loaded by natural frequencies and by compression shocks on suction sides thereof at a certain distance from leading edges thereof, with a flow transition fixation mechanism being provided on the suction side of each compressor blade in a portion of the compressor blade located upstream of an area of action of the compression shocks essentially vertical to a boundary layer flow extending at a compressor blade surface which limits oscillation of a flow transition point between an initially laminar end subsequently turbulent boundary layer flow and, thus, oscillation of the compression shocks, and suppresses their reaction on first and second bending modes as well as on a first torsional mode of the compressor blade occurring under certain conditions of flight. 
   
   
     2. A compressor in accordance with  claim 1 , wherein the flow transition fixation mechanism is provided in a long partial area of the compressor blade extending from the blade tip. 
   
   
     3. A compressor in accordance with  claim 2 , wherein the flow transition fixation mechanism extends essentially parallel to the leading edge. 
   
   
     4. A compressor in accordance wit  claim 3 , wherein the flow transition fixation mechanism comprises an elongated area of surface roughness. 
   
   
     5. A compressor in accordance with  claim 4 , wherein the surface roughness is provided by a fine-grained material which is retained in a raised binder layer. 
   
   
     6. A compressor in accordance with  claim 4 , wherein the surface roughness is provided by a coarse-grained material which is bonded immediately to the blade surface with a binder. 
   
   
     7. A compressor in accordance with  claim 4 , wherein the surface roughness for the flow transition fixation mechanism is provided by protrusions made in the blade material end formed onto the surface of the compressor blade. 
   
   
     8. A compressor in accordance with  claim 7 , wherein the protrusions are triangular in top view. 
   
   
     9. A compressor in accordance with  claim 8 , wherein at least two rows of triangular protrusions which are offset from each other are provided. 
   
   
     10. A compressor in accordance with  claim 4 , wherein the surface roughness is provided by at least one groove extending transversely to the boundary layer flow. 
   
   
     11. A compressor in accordance with  claim 10 , wherein the groove has a semi-circular cross-section. 
   
   
     12. A compressor in accordance with  claim 10 , wherein the cross-section of the groove gradually tapers towards the blade surface in the direction of flow. 
   
   
     13. A compressor in accordance with  claim 4 , wherein the surface roughness is provided by holes made in the compressor blade. 
   
   
     14. A compressor in accordance with  claim 5 , wherein the material providing the surface roughness and the binder used have high erosion resistance. 
   
   
     15. A compressor in accordance with  claim 4 , wherein the flow transition fixation mechanism is dimensioned and positioned such that surge and stall behavior of the compressor blade is not compromised throughout a total specified Reynolds number range from 0.5×10 6  to 5.0×10 7 . 
   
   
     16. A compressor in accordance with  claim 4 , wherein the flow transition fixation mechanism is dimensioned and positioned such that surge and stall behavior of the compressor blade is not compromised throughout a total specified Reynolds number range from 0.5×10 6  to 8.0×10 6 . 
   
   
     17. A compressor in accordance with  claim 4 , wherein the width of the flow transition fixation mechanism  4  ranges between 3 and 15 millimeters and the height/depth ranges between 0.1 and 0.3 millimeters. 
   
   
     18. A compressor in accordance wit  claim 1 , wherein the flow transition fixation mechanism comprises an elongated area of surface roughness. 
   
   
     19. A compressor in accordance with  claim 18 , wherein the surface roughness is provided by a fine-grained material which is retained in a raised binder layer. 
   
   
     20. A compressor in accordance with  claim 18 , wherein the surface roughness is provided by a coarse-grained material which is bonded immediately to the blade surface with a binder. 
   
   
     21. A compressor in accordance with  claim 18 , wherein the surface roughness for the flow transition fixation mechanism is provided by protrusions made in the blade material and formed onto the surface of the compressor blade. 
   
   
     22. A compressor in accordance with  claim 21 , wherein the protrusions are triangular in top view. 
   
   
     23. A compressor in accordance with  claim 22 , wherein at least two rows of triangular protrusions which are offset from each other are provided. 
   
   
     24. A compressor in accordance with  claim 18 , wherein the surface roughness is provided by at least one groove extending transversely to the boundary layer flow. 
   
   
     25. A compressor in accordance with  claim 24 , wherein the groove has a semi-circular cross-section. 
   
   
     26. A compressor in accordance with  claim 24 , wherein the cross-section of the groove gradually tapers towards the blade surface in the direction of flow. 
   
   
     27. A compressor in accordance with  claim 18 , wherein the surface roughness is provided by holes made in the compressor blade. 
   
   
     28. A compressor in accordance with  claim 19 , wherein the material providing the surface roughness and the binder used have high erosion resistance. 
   
   
     29. A compressor in accordance with  claim 18 , wherein the flow transition fixation mechanism is dimensioned and positioned such that surge and stall behavior of the compressor blade is not compromised throughout a total specified Reynolds number range from 0.5×10 6  to 5.0×10 7 . 
   
   
     30. A compressor in accordance with  claim 18 , wherein the flow transition fixation mechanism is dimensioned and positioned such that surge and stall behavior of the compressor blade is not compromised throughout a total specified Reynolds number range from 0.5×10 6  to 8.0×10 6 . 
   
   
     31. A compressor in accordance with  claim 18 , wherein the width of the flow transition fixation mechanism  4  ranges between 3 and 15 millimeters and the height/depth ranges between 0.1 and 0.3 millimeters. 
   
   
     32. A compressor blade for an aircraft engine compressor, which, under operating conditions, is loaded by natural frequencies and by compression shocks on a suction side thereof at a certain distance from a leading edge thereof, with a flow transition fixation mechanism being provided on the suction side in a portion of the compressor blade located upstream of an area of action of the compression shocks essentially vertical to a boundary layer flow extending at a compressor blade surface which limits oscillation of a flow transition point between an initially laminar and subsequently turbulent boundary layer flow and, thus, oscillation of the compression sbocks, and suppresses their reaction on first and second bending modes as well as on a first torsional mode of the compressor blade occurring under certain conditions of flight. 
   
   
     33. A compressor blade for an aircraft engine compressor, comprising a flow transition fixation mechanism on a suction side thereof in a portion of the compressor blade located upstream of an area of action of compression shocks on the compressor blade essentially vertical to a boundary layer flow extending at a compressor blade surface, the flow transition fixation mechanism limiting oscillation of a flow transition point between an initially laminar and subsequently turbulent boundary layer flow and, thus, oscillation of the compression shocks. 
   
   
     34. A compressor blade for a gas torbine, comprising a flow transition fixation mechanism on a suction side thereof in a portion of the compressor blade located upstream of an area of action of compression shocks on the compressor blade essentially vertical to a boundary layer flow extending at a compressor blade surface, the flow transition fixation mechanism limiting oscillation of a flow transition point between an initially laminar and subsequently turbulent boundary layer flow and, thus, oscillation of the compression shocks.